1. Field of the Invention
The invention relates to a device for processing a porous filtration medium, having a holding part which can be mounted on a lower part, wherein an outer wall of the holding part can be positioned outside a surface, which can be used for filtration, of the filtration medium, and a fixing edge which is arranged in the holding part can be positioned on an edge of the filtration medium.
The invention also relates to a method for processing a porous filtration medium, in which method a holding part of a device is mounted on the filtration medium which is arranged in a lower part of a filtration device and which is exposed to a liquid sample, wherein a fixing edge which is arranged in the holding part is connected to an edge of the filtration medium and is raised, together with the filtration medium connected thereto, from the lower part.
2. Description of the Related Art
In the field of the analysis of liquids and gases, various processing methods have become established which use porous media such as filters and diaphragms. For example, the filtration method has become established for the depletion and concentration of dissolved or particulate components. Said concentration is usually necessary because the concentrations of the impurities are too low to carry out direct evaluations. The filtration methods serve as a preliminary stage for further analytical methods, such as optical evaluations, and also for further physical and chemical reactions for signal enhancement.
For newer, more sensitive analysis methods such as PCR (“Polymerase Chain Reaction”) or mass spectrometry analysis, only very small sample volumes can be used. To be able to filter the in many cases typical sample volumes of more than 100 ml for the purpose of concentration, use is typically made of filtration diaphragms of 47 mm or 25 mm diameter. Even after the filtration, when the components or particles are present in concentrated form on the filtration diaphragm, the particles bound to the diaphragm cannot be supplied directly for analysis owing to the diaphragm size. It is necessary to transfer the retained components into a sample volume. If the sensitivity of the methods is to be fully utilized, said volumes must be as small as possible. Volumes of less than 1 ml, preferably 100 μl to 1 μl, are desirable, because, for example for PCR analysis, use is typically made of volumes of 20 μl to 1 μl, and the corresponding unused sample residual quantities come at the expense of sensitivity.
DE 10 2008 005 968 A1 discloses a nutrient medium unit and a method for receiving a filter from a filtration device. Here, the nutrient medium unit is composed of a cover or a holding part, which forms the actual transfer unit, and of a lower part which is filled with nutrient medium. Here, the upper part, which is formed as a holding part, has a fixing edge which, for the removal of the filtration medium from the filtration or processing device, can be connected to an edge of the filter by means of an adhesive bond.
DE 10 2008 005 968 A1 furthermore discloses a method for the microbiological examination of liquid samples, in which a cover or a holding part of a nutrient medium unit is mounted by way of a fixing edge on a filter which is arranged in a lower part of a filter or processing device and which is formed as a diaphragm filter. Here, the fixing edge of the holding part is connected to an edge of the filter by means of an adhesion layer.
The holding part is subsequently raised together with the filter from a filter support of the lower part of the filter device, and placed on a surface of a nutrient medium arranged in a lower part of a nutrient medium unit, wherein the cover or the holding part covers the shell-shaped lower part.
A disadvantage of the known filtration units and of the corresponding methods which have proven themselves for classic microbiological diaphragm applications, and which involve merely the removal of particles or, in the field of microbiology, the visual evaluation of colonies which have formed, is however that, after the filtration, the retained particles or the components thereof can no longer be removed from the diaphragm by flushing in such a way as to form highly concentrated suspensions.
Said disadvantages are of significance in particular in applications which do not correspond to the classic growth of retained germs on agar, but which rather use the modern molecular-biological marking and detection methods, regardless of whether these methods require pre-incubation or are examined directly by marking or enhancement methods.
DE 20 2004 005 694 U1 discloses an apparatus system for liquid testing, which apparatus system has, on a frame, a suction connecting piece to which is fastened, via an adapter, a filter bracket with a filtration diaphragm or a filtration medium, wherein a removable funnel is situated on the filter bracket. After a filtration process, the funnel is removed, and a DNA binding column is inserted, for further testing, between the suction connecting piece and adapter.
It is a disadvantage here that it is not possible for a universal filtration device or processing device to be used. It is also a disadvantage that, during the individual manipulations, there is the risk of contamination. It is also a disadvantage that reverse flushing of the filtration medium is not possible.
EP 1 566 209 A1 discloses a device and a method for vacuum-assisted affinity chromatography.
Here, too, a special device is required in which, furthermore, different exchangeable parts yield the risk of cross-contamination. In said device, too, as in the other devices, reversible flushing is not easily possible without removing the filtration medium.
It is therefore an object of the present invention to provide a device and a method with which it is possible for a porous filtration medium to be inserted in a simple and cheap manner, without further technical aids, into a further processing station in which, by means of the reverse filtration of a very small quantity of liquid, a large amount of the retained components can be transferred, in highly concentrated form, into a small volume.